This invention relates to an arrangement of cooperatively driven hydraulic motors for use in powering an automotive cooling fan or the like. Automotive engines are typically supplied with a liquid coolant, which is circulated through a radiator. The radiator is a heat exchanging device which collects heat generated by an internal combustion process and radiates it to the ambient air. Under ideal conditions, the heat transfer would proceed at the rate at which it is generated. Unfortunately, this is easier said than done.
When an automotive engine is idling, there is no natural airflow across the radiator surfaces, and it is customary to supplement the airflow with forced air from a cooling fan. As an automotive vehicle moves forward from an idle condition and gains speed, it suffers gradually increasing energy losses from air drag, road friction and internal frictional losses. These energy losses are made up by increasing the rate of internal combustion. That in turn increases the rate of heat generation, thereby increasing the work which must be done by the radiator. However, increases in vehicle speed cause an increase in the natural airflow through the radiator. This increase in natural airflow increases natural cooling at a rate which rises faster than the rate of heat generation. As a consequence, the workload on the cooling fan generally decreases with vehicle speed.
The above energy considerations are discussed in detail in Buschur U.S. Pat. No. 5,561,978. That patent teaches that improved energy efficiency may be achieved by providing an automotive cooling system having a plurality of hydraulic motors which are switched into driving relationship with the cooling fan in response to pressure conditions in the hydraulic fluid supply. By way of example, the Buschur patent teaches a hydraulic motor system comprising two segregated spur gear hydraulic motors, communicating with a hydraulic fluid supply and driving a common fan shaft. It is taught that the fluid supply lines may be connected either in parallel or in series and that one or more clutches may be provided for selectively placing the hydraulic motors into driving relationship with the fan shaft. The patent also suggests the use of gerotor type hydraulic motors.
FIG. 1 hereof illustrates a prior art hydraulic motor drive 300 for an automotive cooling fan (not illustrated). The drive unit 300 comprises a first hydraulic motor 302 and a second hydraulic motor 304, both of which are of the gerotor type. Hydraulic motors 302, 304 are supported by a manifold body 306 and are sealed against opposite faces of a coupling block 308. The assembly is secured to manifold body 306 by four bolts 309a-309d and an end plate 310. It is readily apparent that motor system 300 is quite complex, difficult to assemble and susceptible to fluid leakage at approximately a dozen seals to atmosphere. There is a need for an improved dual displacement hydraulic motor system which is more simple to manufacture and easier to maintain.
This invention provides an improved motor system, suitable for driving an automotive cooling fan or the like. In a first aspect, the motor system has two hydraulic drive mechanisms, circumferentially fixed to a common shaft and surrounded by a common, fluid-tight chamber, In this first aspect, the hydraulic drive mechanisms preferably are gerotor sets, each comprising an inner rotor, circumferentially fixed to the common shaft, and an outer rotor eccentrically positioned about the inner rotor. The fluid-tight chamber is established by securing an end frame can against the perimeter of a manifold cavity. The two gerotor sets are stacked on opposite sides of a center plate, one gerotor set being placed in the manifold cavity, and the center plate and other gerotor set being placed in the can.
In a second aspect, the invention provides an improved method of preventing leakage of hydraulic fluid from a dual drive hydraulic motor system. The method involves the steps of:
(1) stacking the hydraulic motor components against a manifold,
(2) placing a sealing ring around the hydraulic motor components and in contact with the manifold,
(3) moving an end frame can enclosingly about the hydraulic motor components and into contact with the sealing ring,
(4) urging a resilient cover plate toward the end frame can from a position opposite the manifold, and
(5) adjustably clamping the resilient cover against said manifold until the resilient cover has undergone a predetermined amount of elastic deformation.
It is therefore an object of the invention to provide an improved dual displacement hydraulic motor system which is more simple to manufacture and easier to maintain.
It is another object of the invention to provide an improved method of assembling a hydraulic motor system.
Other and further objects and advantages of the invention will be apparent from the following specification, with its appended claims, and the attached drawings.